There have been strand cutting machines which produce finely cut materials such as pellets by cutting strands made of synthetic resin and the like which are linear in shape.
One example of this type of strand cutting machine is disclosed in Japanese Unexamined Published Application No. Tokkai Hei 4-226303 (Patent Application No. Hei 3-95089) filed by the present inventor. This strand cutting machine comprises a rotary blade assembly having a plurality of rotary blades which are radially arranged on a rotary plane, a stationary blade unit having a stationary blade which is disposed in front of the rotary plane of the rotary blades and a guide portion for guiding the front ends of the strands in an axial direction of a rotary shaft of the rotary blades; and a take up roller which takes up the strands in front of the guide portion.
The strand cutting machine is capable of cutting the strands on a plane which is parallel with the rotary plane of the blades since it conveys the strands in an axial direction of the rotary shaft. Accordingly, it is capable of smoothly cutting the strands.
However, since the face of the rotary blade on the side of the stationary blade is located on the same rotary plane of the blade edges of the rotary blades, it has a large area which is in contact with the strands and it wipes and abrades the cut areas of the strands. Accordingly an additional force is necessary to perform cutting.
The strands to be cut have various properties such as hard and soft properties depending upon the material. It is difficult for the strand cutting machine to cut the strands having some properties. A problem will arise that conveying of the strands can be smoothly achieved due to the fact that the strands are low in rigidity, but are more liable to become stuck to the surface of a member constituting a conveying path when the strands have softer properties. Since the soft strands are liable to stick to a rotary blade immediately after being cut, rotation of the strands stuck to the rotary blade is liable to occur. Accordingly, a problem will arise that the strands stuck to the rotary blade are cut again. This causes cut strands which are smaller in size than those of the specified cut strands to be mixed with the normally cut strands, resulting in reduction in precision of products.
This phenomenon is more liable to occur as the contact area between the rotary blade and the strands become larger. Adhesion of resin and the like upon the rotary blade is liable to occur when the contact area between the rotary blade and the strands becomes larger. As a result, a problem will arise that the surface of the blade is liable to become contaminated with foreign material.
The strands having a low rigidity will be bent, or undulated when they are urged toward the rotary blade and are unable to advance in a direction normal to the rotary blade. This causes a problem that the cut section is inclined.
When strands made of hard material such as glass are cut, needle-like finely divided fragments may be scattered. If the scattered finely divided fragments become suspended in air, they will have a harmful effect on a human body which inhales them. Therefore, it is preferable to cut such type of strands at a temperature which is as high as possible, and at which less finely divided fragments will be scattered.
However, since cutting at a high temperature will soften hard material, a problem similar to the above mentioned case of soft material will arise.